This application claims the priority of German application 101 57 085.6, filed Nov. 21, 2001, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a stabilizer arrangement for a motor vehicle having a torsion bar with two bar parts, the bar parts including first ends which can each be connected with a wheel suspension of a wheel axle having two wheels. A clutch, with a first clutch element and a second clutch element, form-lockingly connects or separates two second ends of the bar parts situated adjacent to one another. Each of the clutch elements, for a form-locking connection, has at least two form closure elements and, when the clutch is separated, is rotatable relative to the other. An operating device is also provided for separation of the clutch.
A stabilizer arrangement of the above-mentioned type is known from German Patent Document DE 199 23 100 C1. This arrangement includes a two-part torsion bar with two bar parts which can be connected by way of their first ends with a wheel suspension of a wheel axle having two wheels. The second, mutually adjacent ends of the bar parts can be form-lockingly connected by way of a clutch for transmission of a torsional moment and separated when no torsional moment is to be transmitted. For this purpose, the clutch has first and second clutch elements, each of which, for the form-locking connection, has at least two rigid form-locking elements. When the clutch is separated, the two clutch elements can be rotated relative to one another, whereby the two bar parts of the torsion bar are uncoupled and thus reduce stabilization of the rolling motion of the vehicle. For operating the clutch device, the stabilizer arrangement also includes an operating device which separates the two clutch elements from one another. In the known stabilizer arrangement, the operating device includes a hydraulic cylinder which is connected by way of a valve arrangement with a flow medium pump or a tank for hydraulic fluid. The hydraulic cylinder operates one of the two clutch elements in the axial direction, whereby both form closure elements of this one clutch element are simultaneously pulled out of the form closure elements of the other clutch element. In this case, it is a disadvantage that, when the torsion bar is twisted, one form closure element of the one clutch element may be clamped in between the two other form closure elements of the other clutch element. In some cases, therefore, high operating forces have to be applied for separating the clutch. In addition, high technical expenditures are required for the operating device, for example, for hydraulic valves, hydraulic lines, the pump, etc. This results in a high weight and high costs.
It is therefore an object of the invention to provide a stabilizer arrangement of the initially mentioned type which permits a play-free transmission of the torsional moment in the torsion bar while the clutch is connected and which can be shifted by way of an operating device which has to apply lower driving or operating forces in comparison to the prior art.
This object is achieved by way of a stabilizer arrangement for a motor vehicle in which the form closure elements of the first clutch element or the second clutch element form engaging elements movably linked thereto, and in which, for separation of the clutch, the engaging elements are disposed to be movable independently of one another and are displaceable independently of one another by the operating device. Additional characteristics of the invention are reflected in dependent claims.
Principal advantages achieved by the invention include disengagement of the engaging elements almost without force, and therefore also with a much lower operating force, from the form closure elements during separating of the clutch. This, in addition, results in a low wear on the clutch. Furthermore, the operating device for the form closure elements or engaging elements may have a compact construction because no high operating forces have to be applied. These advantages are achieved, in each case, by disengaging the engaging element from the form closure element which at that moment experiences no circumferential force generated during the rotation of the torsion bar. The clutch is therefore always opened without any load.
If several form closure elements are arranged in a row, with several form closure elements forming one form closure section, respectively, and, in each case, interacting with the engaging elements, then, when the clutch is separated, a reengaging of the two clutch elements can even take place when the two clutch elements are still rotated relative to one another.
In a particularly preferable embodiment, each of two form closure sections, together with the engaging elements assigned to them, forms one respective rotation blocking device. Two rotation blocking devices form a blocking device pair. However, each of the rotation blocking devices causes rotational blocking in only one relative rotating direction between the clutch elements. In the other relative rotating direction, each rotation blocking device is free running. The rotation blocking direction and the free running direction of one rotation blocking device are in each case oriented opposite to the rotational blocking direction and the free running direction of the other rotation blocking device. By means of this, in a particularly advantageous manner, restoring of the starting position of the two clutch elements, rotated relative to one another, is permitted.
In a preferred embodiment, the engaging elements are maintained in engagement with the form closure elements, even when the operating device malfunctions, so that a so-called fail-safe function is provided.
In order to be able to displace the engaging elements independently of one another by way of the operating device without a high operating force, a prestressable operating spring is provided for the engaging elements. Although both engaging elements are acted upon by way of the spring force when the operating spring is prestressed, the engaging element, which at this moment experiences no circumferential force, is disengaged from the form closure elements so that movement of this engaging element takes place easily. In this case, the operating spring is prestressed such that the spring prestressing force provided is greater than the force of the holding spring and smaller than the force to be applied which would be necessary for swivelling an engaging element subjected to circumferential force. When prestressing of the operating spring is reduced again, the holding springs will bring the engaging elements back into engagement with the form closure element, and the clutch is closed again. Instead of indirect operation of the engaging elements by way of the operating spring by means of only one operating device, several operating devices which can be controlled independently of one another may be provided. In this case, one operating device can be assigned to each engaging element.
According to one aspect of the invention, prestressing of the operating springs takes place by way of the operating device, which may comprise an electric motor drive and a shifting element, so that the operating device is cost-effective and, in addition, can be integrated into the clutch in a compact construction.
In one particularly preferred embodiment, the form closure sections are implemented by toothing sections with several teeth situated behind one another. These teeth form the form closure elements of the first clutch element. The engaging elements of the second clutch element are constructed as detent pawls which are disposed to be movable relative to the respective toothing section and have at least one detent. While its size is small or the space requirement for swivelling the detent pawls out is low, this embodiment permits a good torque transmission between the two clutch elements.
Free running in one relative rotating direction and rotational blocking in the other relative rotating direction as mentioned above are achieved in a simple manner by way of the flank shape of the teeth and the detent. The flank shape is constructed to be self-locking in the rotation blocking direction and, in the free running direction, has a contour which promotes displacement movement of the detent pawl, which displacement movement causes disengagement of the detents from the toothing sections. During relative rotation between the first and second clutch elements in the free running direction, the corresponding detent pawl is lifted by the flank shape over the individual teeth. In the other rotating direction, the detent pawl is held on the respective tooth, whereby torque transmission between the two clutch elements can take place in this rotating direction.
It was found to be particularly advantageous for the toothing sections to be constructed as respective saw toothings in which each tooth has two flanks of different steepnesses. The two toothing sections of a rotation blocking device are in this case oriented in opposite directions so that the free running or self-locking mentioned above is obtained by way of the saw tooth shape.
In the following, the invention will be explained in detail with reference to embodiments shown in the drawing.